When a received signal is demodulated, it is necessary to correct (hereinafter, ‘equalize’) the phase and amplitude of the received signal to compensate for channel distortion and fading. In particular, when channel distortion is large and when the channel characteristics vary greatly over time, there is a need for techniques to improve equalization accuracy and techniques that ensure tracking of rapid changes in the channel.
There are two general types of equalization: time domain equalization and frequency domain equalization. Time domain equalization is an equalization method that feeds the received signal into an adaptive filter and compensates for distortion of the received signal while optimizing the filter coefficients by use of an adaptive algorithm. Frequency domain equalization is an equalization method that detects a CIR (Channel Impulse Response) in the time domain on the basis of the received signal, performs a Fourier transform on the detected result, and performs waveform equalization in the frequency domain. In the ATSC (Advanced Television Systems Committee) broadcasting standard using VSB modulation, which has been adopted in North America, for example, a known PN code signal is inserted as a field synchronization signal in specified data frames, so there are known methods of frequency domain equalization that perform CIR detection by using this known signal as a reference signal (see, for example, patent reference 1 and patent reference 2).